Parkinson's disease (PD) is a chronic neurodegenerative illness that causes progressive disability due to rigidity, bradykinesia, postural instability and often tremor at rest. It results from loss of dopaminergic neurons in the substantia nigra and affects an estimated 500,000 to I million people in North America. Some 20,000 to 50,000 new patients are diagnosed each year. Care of these patients and lost productivity cost at least $14 billion per year. Although PD symptoms respond to dopamine precursor by treatment with levodopa, a precurser of dopamine, the disease continues to progress, resulting in increasing lack of mobility and decreased functioning. Identification of a medication that slows or reverses the neuronal destruction that occurs in PD would be a major advance in the treatment of this devastating illness. At this time, only selegiline (Eldrepyl), a selective monoamine oxidase-B (MAO-B) inhibitor has been approved by the US Food &Drug Administration as a possible neuroprotective agent in PD, however, subsequent studies have suggested that most of the benefit of selegiline is actually symptomatic, related to its metabolism to an amphetamine-like molecule, and not due to true neuroprotection.The purpose of PD Neuroprotection Clinical Trial is to establish some 42 clinical centers through which clinical trial protocols can be planned and carried out using candidate neuroprotective drugs, with the goal of identifying agents that might slow, and even reverse the progressive course of PD. The candidate medication(s) to be tested and the clinical protocol(s) to be followed will be determined from collaboration and consensus among the 42 participating centers. Approval of the Duke Medical Center Internal Review Board (IRB) will be obtained prior to starting any clinical trial at Duke.